Netdev Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 0/9] Add support for type-based and enum value-based CO-RE relocations
Date: Tue, 18 Aug 2020 22:32:41 -0700	[thread overview]
Message-ID: <CAEf4BzZG7fi4fZLW4O_OB4tueGjX8jz3PdX7iFNjCi9zZc6QQg@mail.gmail.com> (raw)
In-Reply-To: <20200819013703.cgbty6b6ufp7wuqm@ast-mbp.dhcp.thefacebook.com>

On Tue, Aug 18, 2020 at 6:37 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Aug 18, 2020 at 06:31:51PM -0700, Andrii Nakryiko wrote:
> > On Tue, Aug 18, 2020 at 6:21 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > On Tue, Aug 18, 2020 at 03:39:12PM -0700, Andrii Nakryiko wrote:
> > > > This patch set adds libbpf support to two new classes of CO-RE relocations:
> > > > type-based (TYPE_EXISTS/TYPE_SIZE/TYPE_ID_LOCAL/TYPE_ID_TARGET) and enum
> > > > value-vased (ENUMVAL_EXISTS/ENUMVAL_VALUE):
> > > >
> > > > LLVM patches adding these relocation in Clang:
> > > >   - __builtin_btf_type_id() ([0], [1], [2]);
> > > >   - __builtin_preserve_type_info(), __builtin_preserve_enum_value() ([3], [4]).
> > >
> > > I've applied patches 1-4, since they're somewhat indepedent of new features in 5+.
> > > What should be the process to land the rest?
> > > Land llvm first and add to bpf/README.rst that certain llvm commmits are necessary
> > > to build the tests?
> >
> > Clang patches landed about two weeks ago, so they are already in Clang
> > nightly builds. libbpf CI should work fine as it uses clang-12 nightly
> > builds.
> >
> >
> > > But CI will start failing. We can wait for that to be fixed,
> > > but I wonder is there way to detect new clang __builtins automatically in
> > > selftests and skip them if clang is too old?
> >
> > There is a way to detect built-ins availability (__has_builtin macro,
> > [0]) from C code. If we want to do it from Makefile, though, we'd need
> > to do feature detection similar to how we did reallocarray and
> > libbpf-elf-mmap detection I just removed in the other patch set :).
> > Then we'll also need to somehow blacklist tests. Maintaining that
> > would be a pain, honestly. So far selftests/bpf assumed the latest
> > Clang, though, so do you think we should change that, or you were
> > worried that patches hadn't landed yet?
>
> I was hoping that libbpf.h can have builtins unconditionally, but selftests can
> do feature detection automatically and mark them as 'skip'.
> People have been forever complaining about constant need to upgrade clang.
> In this case I think the feature is not fundamental enough (unlike the first
> set of builtins) to force adoption of new clang.
> If/when we start using these new builtins beyond selftests
> that would be a different story.

Ok, took some tinkering to do this for btf_type_id() tests, but
everything works now as you described above. Posted v2.

      reply	other threads:[~2020-08-19  5:32 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-18 22:39 Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 1/9] libbpf: improve error logging for mismatched BTF kind cases Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 2/9] libbpf: clean up and improve CO-RE reloc logging Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 3/9] libbpf: improve relocation ambiguity detection Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 4/9] selftests/bpf: add test validating failure on ambiguous relocation value Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 5/9] libbpf: implement type-based CO-RE relocations support Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 6/9] selftests/bpf: test TYPE_EXISTS and TYPE_SIZE CO-RE relocations Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 7/9] selftests/bpf: add CO-RE relo test for TYPE_ID_LOCAL/TYPE_ID_TARGET Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 8/9] libbpf: implement enum value-based CO-RE relocations Andrii Nakryiko
2020-08-18 22:39 ` [PATCH bpf-next 9/9] selftests/bpf: add tests for ENUMVAL_EXISTS/ENUMVAL_VALUE relocations Andrii Nakryiko
2020-08-19  1:21 ` [PATCH bpf-next 0/9] Add support for type-based and enum value-based CO-RE relocations Alexei Starovoitov
2020-08-19  1:31   ` Andrii Nakryiko
2020-08-19  1:37     ` Alexei Starovoitov
2020-08-19  5:32       ` Andrii Nakryiko [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAEf4BzZG7fi4fZLW4O_OB4tueGjX8jz3PdX7iFNjCi9zZc6QQg@mail.gmail.com \
    --to=andrii.nakryiko@gmail.com \
    --cc=alexei.starovoitov@gmail.com \
    --cc=andriin@fb.com \
    --cc=ast@fb.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=kernel-team@fb.com \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCH bpf-next 0/9] Add support for type-based and enum value-based CO-RE relocations' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).